Friday 30th January
Thursday was another unsettled day with a cool breeze from the east-southeast for much of the period with the cloud thickening during the afternoon. Another weather front crossed our area during darkness, however, it became fragmented as it made its way across southern England and produced less rain than was forecast. The first spots from the advance rain-band were noted at 22.20 with the main rain arriving just before 03.00 that added 2.0mm to the January total now standing at 156.7mm being 175% of my 42-year record.
The temperature by day was depressed due to the cloud cover and lack of any sunshine that gave us a maximum of 6.4C at 13.15 during a brief period of brighter weather. The high was 0.7C below my long-term average. There was little variation overnight with a minimum of 4.6C logged at 19.50. After that time the temperature eased homewards due the advancing cooed from the next depression. The diurnal range of temperature was therefore, just 1.8C.
Friday began with total cloud cover again, the thermometer having risen to 6.7C by 08.00. There will be a replay of the past twenty-four hours today as another low-pressure systems edges in later today with rain once again probably arriving during the late afternoon, being heavy for several hours overnight.
By tomorrow the synoptic chart shows a collection of seven low-pressure systems to the west, north and immediate east of the UK. An area of high pressure, that was over eastern Europe has consolidated and moved towards Scandinavia. It is, however, continuing to push back on the advancing depressions but not sufficient at the current time to bring very cold conditions. The slight relocation will see the forecast wind direction continue from a southeasterly quadrant over the weekend before likely backing a few degrees to have a more easterly component by Monday with the result that maxima will drop a degree of two to hover around the average.
How does the jet stream work?
The jet stream flows high overhead and causes changes in the wind and pressure at that level. This affects things nearer the surface, such as areas of high and low pressure, and therefore helps shape the weather we see. Sometimes, like in a fast moving river, the jet stream’s movement is very straight and smooth. However, its movement can buckle and loop, like a river’s meander. This will slow things up. making areas of low pressure move less predictably.
The jet stream can also change the strength of an area of low pressure. It acts like a vacuum cleaner, sucking air out of the top and causing it to become more intense, lowering the pressure system. The lower the pressure within a system, generally the stronger the wind, and more stormy the result, as recently.
On the other hand, a slower, more buckled jet steam can cause ares of higher pressure to take charge, which typically brings less stormy weather, light winds and dry weather.